It was thirty years ago this week that the last helicopter left Saigon, leaving us with a final terrible photograph of that terrible war: the helicopter lifting off from atop the American embassy, seemingly tethered to the roof by a chain of human beings desperate to get out.

Declare victory and leave -- I guess that's how you end a modern war. No North Vietnamese delegation in formal attire came to sign instruments of surrender on an American battleship. I guess that was because Communists don't wear formal attire. And because everybody knew they hadn't lost.

A silence about the war settled on all of us. The last of the three presidents who presided over it resigned amid the flames of his own disgrace; his kindly successor, in pardoning him, referred to him as "the man who brought peace to millions," and we all had to stop for a moment to remember what he meant. It took twenty years for us to understand how callous we had been to the soldiers returning from that war, whose presence among us reminded us of something we wanted to forget. Something strangely like relief sprang up when Desert Shield turned into Desert Storm and our smart bombs shot through the air, flying low and unseen toward their targets with deadly precision: we would shower these young soldiers with the love we had withheld from their Vietnam-era counterparts, we would make up for it all now. Yellow ribbons appeared everywhere. Our exit strategy triumphed: quick, clean, out. Our losses were gratifyingly modest: from hostile fire, 122 dead. From friendly fire, 35. Non-combat fatalities, 31. And, as always, we did not count the enemy dead. That would be their concern.

Immediately upon our departure from Saigon, a Vietcong takeover of the government; Saigon was now Ho Chi Minh City. There was a border war with China, even bloodier than the ten year engagement with the Americans, something I hadn't even registered as having occurred until this morning when I heard it on an NPR retrospective. Good Lord.

Thirty years later, Vietnam is at peace and Americans visit as tourists. Once in a while, even now, a group of American MIAs is returned to us: something to bury, at last. Black flags with the silhouette of a POW, his head bowed in discouragement, continue to hang from the flagpoles of American firehouses and police stations, marking the survival of a civic myth that persists thirty years after the war: They are still being held. They still wait for us to come and rescue them. They are still alive.

But I wonder if we don't cling to the POWs for another reason. If it doesn't mean something else, something besides the obvious longing for the return of loved ones. If we admitted that they were gone, then we would be finished. Then there would be no nothing more to do. Not even one more chance to change something -- anything -- about what happened thirty years ago.